Vacuum belt conveyor

ABSTRACT

The invention concerns a vacuum belt conveyor for transferring veneer sheets under a vacuum effect. The conveyor consists of a vacuum box under a vacuum effect, having at least one perforation extending lane-like in the direction of conveyance of the conveyor. Conveying belts are running on both sides of the perforation. The belts are brought into contact with a veneer sheet to be transferred, whereby the veneer sheet and the belts line an underpressurized space, and the sheet is retained in contact with the belts. A lug movable in the direction of the vacuum lane is arranged at the perforation for keeping any jamming debris away.

The invention relates especially to a vacuum belt conveyor for transferring veneer sheets.

The basic structure of the vacuum belt conveyor is conventional, i.e. it consists of an elongated box structure whose interior can be brought under a vacuum effect. At least one lane-like perforation extends along the bottom of the box through which the bottom area of the box can be brought under the vacuum effect prevailing inside the case. The lane is bounded by a conveyor belt running at its both edges in dragging contact with the lower surface of the vacuum box. The product to be conveyed, such as a veneer sheet, is brought, at its upper surface, under the vacuum effect through the openings, the sheet thus being moved by the belts to the intended place where it is released from the vacuum effect by stamping by means of kicker arms provided in the conveyor.

Vacuum belt conveyors have been used to transfer veneer sheets, among other things, even as embodiments in which the veneer sheet lies on the conveyor. A vacuum inside the conveyor affects the lower surface of the veneer sheet holding the sheet pressed against the belts that convey the sheet. Even in these embodiments the belt are placed adjacent to a vacuum area to bound the vacuum area.

The problem with these conveyors has been, particularly when applied to the conveyance of veneer sheets, that different kinds of pieces of sheet end up in the perforation and remain there interfering with the vacuum effect. The perforations must be cleaned at regular intervals, in which operation the usual practice is to stop the devices creating the vacuum in the box. This results in an immediate interrupture in the production.

An improvement has now been achieved to the problems by the vacuum belt conveyor according to the invention, having arranged at the perforation a lug movable in the direction of the lane and in contact with the perforation.

The invention will be explained in more detail with reference to the accompanying drawing in which

FIG. 1 shows an embodiment of the vacuum belt conveyor according to the invention, applied to the stacking of veneer sheets, seen in the direction of conveyance of the veneer sheets,

FIG. 2 shows another embodiment of the vacuum belt conveyor according to the invention, applied to the stacking of veneer sheets as well, seen in the direction of conveyance of the veneer sheets,

FIG. 3 shows a stacking embodiment of the invention, seen transversely to the direction of conveyance of the veneer sheets,

FIG. 4 shows a detail of the embodiment of the vacuum belt conveyor according to FIG. 1,

FIG. 5 shows a detail of the embodiment of the vacuum belt conveyor according to FIG. 2, and

FIG. 6 shows an embodiment of the invention as a conveyor in which the veneer sheets are conveyed on top of the conveyor.

FIGS. 1 to 3 show a vacuum belt conveyor apparatus having a conventional basic structure, applied to the conveyance of veneer sheets, with the sheets hanging from the conveyor. The vacuum box 1 forms a base for the apparatus. The vacuum box is provided with a blower 2 by means of which a vacuum can be maintained in the box relative to the ambient. The lower part of the box is formed into a conveyor box 3 having a vacuum connection with the vacuum box. The lower surface of the conveyor box 3 comprises a slot, or alternatively a line of punched holes or openings, extending in the longitudinal direction of the box, substantially over the length of the box.

The conveyor box 3 is arranged surrounded by two belts 4 formed into loops. They move in dragging contact with at least the lower surface of the conveyor box 3, one on each side of the vacuum slot or the line of vacuum openings. When the lower side of the conveyor box 3 is brought into contact with the upper surface of a veneer sheet 5, it closes the vacuum slot or the line of vacuum openings of the conveyor box. The veneer sheet is kept suspended against the belts and travels to the intended place of delivery therewith. There are kicker arms 6 on two sides of the conveyor box by means of which the veneer sheet 5, by kicking it off, can be released from the belts 4 and the vacuum effect that holds it up. The veneer sheet can be put into the intended place, such onto a veneer sheet stack, using this kicker function.

Usually, there are two similar vacuum belt conveyors parallel to each other, as shown in the exemplary FIGS. 1 and 2. A vacuum belt conveyor can also be embodied with one box, in which case the conveyor belts may lie farther away from one another and have several parallel vacuum slots or rows of vacuum holes therebetween. Such a one-box structure is suitable for conveying stiff veneer. The length of the vacuum belt conveyors is adjusted according to the current necessary conveyance distance, which is shown as a mainly schematic illustrative presentation in the views of the accompanying drawing.

FIG. 6 shows a conveyor structure that is principally the same as in FIGS. 1 to 5 but intended to convey the veneer sheets supported on top of the conveyor. To keep the veneer sheets under the control of the conveyor, the structure of the conveyor is embodied principally in the same way as explained above in the case of conveyors in which the veneer sheets hang from the conveyor. The apparatus can be used, for example, to unload sheets from a veneer sheet stack from below.

These vacuum belt conveyors work without problems when the material to be conveyed is unbroken. When conveying veneer, problems are caused by the veneer debris or small size veneer pieces which inevitably end up in the working area of the vacuum belt conveyors along with the whole veneer sheets. These small-sized veneer pieces often settle in the vacuum slot or in the area of the vacuum openings, between the conveyor belts 4. In this space, they obstruct their own area as regards the vacuum effect but do not get under the influence of the kickers 6, for example. The interference must be get rid of, and this usually requires an interruption in the operation because the harmful pieces cannot be removed properly unless the vacuum apparatus is stopped.

An improvement has now been achieved to this problem by the vacuum belt conveyor according to the invention. The basic structure of the vacuum belt conveyor is as described above, i.e. consists of a vacuum box under a vacuum effect, having at least one perforation extending lane-like in the direction of conveyance of the conveyor, as well as conveyor belts running on both sides of the perforation and lining it. The vacuum belt conveyor according to the invention is characterized in that a lug movable in the direction of the vacuum lane is arranged at the perforation.

FIG. 4 shows a part of the end of a vacuum belt conveyor. In this embodiment, the vacuum lane is implemented in the form of a slot extending between the belts 4, in the same direction as them. As an inventive embodiment, a lug 8 is placed in this slot. The lug is designed to stay in the slot by its shape and to be movable back and forth along the length of the slot. To generate this back-and-forth motion, an appropriate drive, such as a cable or chain drive, is placed in the conveyor box part 3. Preferably, the lug protrudes from the lower surface of the conveyor box 3 less than the conveyor belts 4, whereby the lug does not interfere with the movement of the veneer sheet suspended by conveyor belts. The lug 8 pushes the scrap 9, such as a piece of veneer, that has ended up in vacuum slot, to an area which the vacuum effect does not reach, the scrap thus falling out of the apparatus. The lug 8 can also be arranged to follow a circling path inside the conveyor box 3, it then being necessary to create appropriate passageways for the lug at the end and beginning of the vacuum slot, respectively.

FIGS. 5 and 6 illustrate an alternative embodiment of the invention. In this embodiment, the vacuum lane of the conveyor box 3 is implemented in the form of punched holes which lie in two lines between the conveyor belts 4. In this embodiment, the lug 10 is located on the surface of the conveyor box 3, moves along the vacuum lane and wipes the scrap 9 from the surface of the vacuum lane. The lug 10 may be fixed to the conveyor belts 4 and travel around the conveyor box 3 together with them. The embodiment requires such an embodiment of the vacuum box in which the connection to the conveyor box is implemented in another way than in FIGS. 1 to 3. Besides, the lug 10 may have its own drive, such as a cable or chain drive 11, producing a back-and-forth driving motion along the vacuum area, or a circling path of motion, having the returning motion arranged inside the conveyor box 3, through passageways provided in its ends. In the reciprocating driving motion, its must be considered how much the lug may protrude relative to conveyor belts 4. 

1. A vacuum belt conveyor for transferring veneer sheets under a vacuum effect, which conveyor consists of an elongated vacuum box and a means to produce a vacuum effect inside the box, the box being furnished with at least one perforation lane extending along its one surface, as well as with conveying belts arranged to run externally on said one box surface on both sides of the perforation lane in a circling loop, wherein a lug movable in the direction of the perforation lane is arranged at the perforation.
 2. A vacuum belt conveyor as defined in claim 1, wherein said perforation is in the form of a slot and the lug is situated in the slot so as to stay there by its shape.
 3. A vacuum belt conveyor as defined in claim 1, wherein said perforation is in the form of separate holes and the lug is crossing the holes externally in close contact with said one box surface.
 4. A vacuum belt conveyor as defined in claim 1, wherein the lug is moving back and forth at the perforation lane.
 5. A vacuum belt conveyor as defined in claim 1, wherein the lug moves along a circling path at the perforation lane.
 6. A vacuum belt conveyor as defined in claim 2, wherein the lug is moving back and forth at the perforation lane.
 7. A vacuum belt conveyor as defined in claim 3, wherein the lug is moving back and forth at the perforation lane.
 8. A vacuum belt conveyor as defined in claim 2, wherein the lug moves along a circling path at the perforation lane.
 9. A vacuum belt conveyor as defined in claim 3, wherein the lug moves along a circling path at the perforation lane. 